


I'd Love to Hate You but I Can't (Underfell Sans X Reader)

by I_Dont_Carrot_Tall



Category: Undertale (Video Game)
Genre: Alternate Universe - Underfell (Undertale), Anxiety Attacks, Anxiety Disorder, Biting, Depression, Dirty Thoughts, Eating Disorder Not Otherwise Specified, Ecto-Penis (Undertale), Ecto-Tongue (Undertale), Emotional/Psychological Abuse, F/M, Female Frisk (Undertale), Female Protagonist, Implied/Referenced Abuse, Light Bondage, Love, Love/Hate, Mild Blood, Mild Kink, Minor Alphys/Undyne (Undertale), Minor Character Death, Minor Injuries, Oral Sex, Physical Abuse, Reader Is Not Frisk (Undertale), References to Depression, References to Drugs, Resolved Sexual Tension, Smoking, Suicidal Thoughts, Underfell Asgore Dreemurr, Underfell Flowey (Undertale), Underfell Papyrus (Undertale), Underfell Sans (Undertale), Vaginal Fingering, Vaginal Sex
Language: English
Status: In-Progress
Published: 2018-12-08
Updated: 2019-01-16
Packaged: 2019-09-14 13:30:43
Rating: Explicit
Warnings: Graphic Depictions Of Violence
Chapters: 3
Words: 2,372
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/16913745
Author URL: https://archiveofourown.org/users/I_Dont_Carrot_Tall/pseuds/I_Dont_Carrot_Tall
Summary: Your sister Frisk was always the adventurous type. You, being the only one she could look up to, were often dragged into her journeys, not that you minded of course. In fact, it was somewhat refreshing to see her so full of hope and determination, despite everything that was wrong in your lives.When Frisk asks you for permission to go hiking up Mount. Ebbott, however, you find yourself a bit reluctant to agree.After hours of pleading from your sister, you finally find yourself giving in to her request. As long as she stays close to you, everything would be fine...Right?





	1. Chapter 1

**Author's Note:**

> This is my first story on this site, so I'd appreciate any feedback I can get on it, good or bad. I'm a fairly new writer, and this is just a hobby for me, so keep in mind it might not be amazingly written like some other stories on the platform.

There was a dull pain in your skull. A deep throbbing that made it feel like your head was about to split in two. Hazy memories swam at the back of your mind, and from the corner of your eye you could see only red.

Slowly but surely, shapes began to take form, and you could see the edges of what looked to be a cavern, rocks jutting out from the ground, a couple particularly sharp, menacing looking rocks seeming way too close for comfort. The place was also littered with dead leaves and golden flowers that were casually sprinkled around near the circle of warm light that illuminated the scene from somewhere far above you. The sun, you assumed. Specks of dust and pollen danced around in your vision, though it seemed like an abnormal amount of the stuff was in the air. Enough to make you cough and splutter as you inhaled, bringing you back to your senses.

"F...risk...?" Your voice came out hoarse and dry, almost strangled. "W...Where..?" You tried to lift your head, but a sharp heavy feeling made it drop back to the ground and you winced, pain flooding your senses.

The quick thumping sound of footsteps running towards you made you try in vain to look up, but it seemed impossible in your current situation.

"Y/N! You're awake?! I-I was scared that y-you w-were.." Frisk's all too familiar voice rang out, echoing off of the walls. She didn't finish her sentence, leaning down into your line of sight. You could see that she was also hurt from the fall, which you had worked out was the reason you were lying on your back unable to move with the light of the sun poking from a hole in the ceiling; as bandages were lazily strewn around her leg, a small bit of deep red blood seeping through the off white cloth.

You gave Frisk a weak relieved smile, trying again to pull yourself up from the ground. You managed to pull yourself halfway before an insane dizziness came over you, and your limbs threatened to send you back to the cold hard ground. Luckily you were held upright by Frisk, who gave you a deeply concerned, almost frightened look. "Y...Y/N...You're hurt!"

"I...It's fine.." You manage to mumble out through your dazed state, gripping her arm to keep yourself from falling back. "I'm ok.."

Frisk stubbornly shakes her head. "No, no you're not." She looks around , eyes darting around nervously for a moment before looking back at you, seeming more focused. She carefully moves you over to the side, propping you gently up against a rock. 

You try to protest, say you don't need help but Frisk continues anyway, a familiar determination sparking in their eyes. She reaches into and takes a bandage out from her backpack, kneeling down in front of you. "I...Hope this helps.." Frisk gently starts to wrap the bandage around your forehead and around the back of your head, careful not to hurt you further. She does this a few times, before tying a makeshift knot, securing it in place "I-I'm gonna go get help Y/N." Frisk stands up, and you shake your head, despite the pain and lightheadedness that came from it.

"N-No! Frisk...I..It's not safe.." You cough, trying desperately to pull yourself upright.

"I...I can't just leave you like this! I have to get help!" The spark in her eyes burned brighter. There was no stopping her, she was determined. "I'll be right back...I promise." Her words are sincere, and you wished you could believe them..but something about this cave..The atmosphere...Just wasn't right..You didn't want her to go exploring alone..

* * *

You sighed, giving up. "Ok Frisk.." Your eyes didn't quite meet hers. You saw from the corner of your eye that Frisk was giving you a worried look, but then turned on her feet, rushing off despite the injury on her leg.

You glanced upwards, tears glazing your vision. You should never have agreed to this..You knew Mount.Ebbot was dangerous, even if all the stories about monsters weren't true, it was still a deadly mountain...and now you were both trapped underneath it. What if Frisk never came back..? Would you both just die here..? You felt tears run down your face, wanting so badly for this all to be a dream, for you both to wake up in your bed and be safe again. You squeeze your eyes shut tight, trying to stop the tears from racing down your cheeks. It had felt like you had been sitting here for hours, the pain in your head had slowly faded to a dull ache, and you pulled yourself into a crouched position, a few tears escaping your eyes despite your efforts. You almost screamed in frustration. Crying wouldn't fix anything! You told yourself, forcing your emotions back into the recesses of your mind, blocking them out. You had to get up. Find Frisk. You slowly raised your head, a feeling you couldn't describe rising from deep within your gut.

Something burned within you...Telling you to keep moving forward. You weren't dead yet.

Your soul glows brightly with Perseverance, and you force yourself to stand.

 

 

 

* * *

 


	2. Ruins

* * *

* * *

 

You struggled to move forward, but forced yourself to keep going, even though your body was screaming at you to stop. You staggered on until you came to an entryway marked by two pillars on either side, and some sort of emblem/symbol in the middle. You stared up at it...A circle, two spiky wing like shapes on either side, and three small triangles underneath.Two of them symmetrical, but the one at the bottom was upside down. You wondered silently what it meant, and why it was here...Had humans came here before..? Maybe there were humans still living here..? You silently hoped that you were right..Then maybe that meant you and Frisk would be safe. You held onto that thought, pressing forward into what looked like a large room in the cavern, light poking through from an opening in the top, and a small patch of lone grass growing in the middle where the light shone through. The room was freezing cold, and empty. You shivered, not sure what to make of the strange sight.

You hesitantly pushed forward, walking towards the next room.

This room was..Beautiful. In a twisted sense of the word. Wilting Red roses and dead leaves surrounded the area, shrouding it in dark beauty. Cracked tilted staircases leading up onto a platform revealed another entryway at the top, this time in a deep dark red marble like structure, the same emblem still boasted in the middle. You could see yet another room beyond this one, and started to wonder silently what this was meant to be, when you realized something. It looked old, like hundreds of years old.. You placed a hand on the cracked marble of the pillar, running your hands across the ridges. To your surprise, it actually felt pretty warm, almost electric. It brought a certain sense of twisted comfort along with it. If it was warm..Surely that meant there were still people here...Right? You felt yourself relax a little more, but couldn't shake the nagging feeling you got at the back of your mind, one that was telling you that something was way off..

Approaching the next room, you saw..A puzzle of some sort? Whatever it was, it had been solved already by vines? They seemed to be pushing against 4 of the 8 buttons deliberately, solving the puzzle for you. You gave them a curious look. The vines, like most plant life in this place, appeared to be badly malnourished, but certainly weren't dead. You wondered to yourself how the vines had gotten here, as there didn't appear to be any dirt for them to grow through. You shook your head. That wasn't important. You had to find Frisk.

More and more rooms. So many it looked like at one point there had been an entire civilization living here. Every room appeared to fulfil a purpose of some sort, most littered with deadly puzzles and traps which, luckily enough for you either didn't seem to work or were already solved...By vines. The rooms were all different, all stood out separately, but there were a few similarities between them that stuck out. Almost every room had that symbol hidden somewhere, whether it be an opening or simply just on one of the walls, One of the bizarre constants in every single room that had taken you a while to notice at first had quickly became a nagging question in the forefront of your mind. Why did they all consist of only black, red and yellow...? It made you stand out a bit, as you were wearing a (F/C) hoodie with a (SF/C) shirt.

You pause midstep, hearing...something..It sounded like...shuffling... You turn around. It doesn't look like there's anything-

Tch-tch-tch- 

Your vision suddenly cuts out repeatedly, flashing from complete darkness and back to normal again for a couple of seconds, your body starting to feel heavier. A glowing purple heart shape appears in front of you...Wait did it just come out of you..? You stare, enamoured by the sight in front of you, though your amazement soon turned into shock as you absorbed the sight that had just appeared in front of you. The only colours you could see were black, red and yellow, and in those three colours, stood three different shapes, barely recognizable..and definitely not human. You stumbled backwards, covering your mouth to stifle a gasp. You tensed, remembering everything that you'd heard about the creatures under the mountain. They were without mercy...They were ruthless..Animals..

You tried to run, but to no avail. It did nothing. It was almost like they were holding you in place. Was this really how you were gonna die..? You braced yourself..This was it..It was all over now.

You barely had time to react as magical bullets pierced the purple heart one by one, which seemed to have faded into a dull greyish purple, you felt pain shooting through your very essence, making you fall to your knees. "H-Help!" You call desperately into the darkness, but it was too late. You felt yourself slip away into unconsciousness as more and more bullets fired into the heart without mercy, your eyes closing over as you collapse onto the cold hard stone below.

>  


	3. Home?

**Notes for the Chapter:**

> I didn't forget about this! I've just been busy and this has been sitting here almost complete for months so I thought I'd post it to revive it.

You woke up with a start, almost screaming but you bit your tongue, remembering where you were...and what had happened. It felt like you had been out for hours. You rubbed your eyes, realising only now that you were laying on something soft, comfortable...A bed...?Your eyes trailed around the walls of the strange place, which was a room of some sort, almost like a little child's. Stuffed toys were lying all around the floor, somewhat morbid in appearance though, and everything was still in that same dark colour scheme. 

You tried to stand up, surprisingly managing to do so with relative ease. It was almost like your injuries had been completely healed...You stretched out your limbs, yawning quietly. You still had to find Frisk. You took a step forward, but stopped, looking down in confusion as your foot made contact with something on the ground. It appeared to be a pie of some sort sitting atop a metal plate, but it looked...awful. You gagged at the sight. You weren't hungry right now anyway, but the sight of dead snails locked into a pie certainly wasn't making you any hungrier.

You ignored the pie, leaving it on the ground and walking to the door, slowly and cautiously creaking it open a slither, looking out. 

The door lead into a red hallway with black carpeting, and yellow lights illuminating the area in an eerie yet warm and inviting glow, making you feel conflicted with the two contrasting feelings that arose within you. You slowly step out, the floorboards making an audible creaking sound as you set foot on them, cringing at the noise.

"Oh..Child. You are awake!" A voice echoed out from somewhere in the distance, not too far off. It was somewhat motherly, although something about it's tone seemed...off. "Come here. Young one, I do not bite." You heard a quiet giggling from the same direction, and you felt a shiver go through your spine, keeping your body tense. You didn't dare take another step, instead uttering out. "W-Where's my sister?" You had meant to sound demanding, but your voice barely came out as a hoarse whisper, nevermind any sort of authoritative tone. 

"Oh, that other human child? I let them leave a while ago, but they told me to find you and keep you safe.." 

You didn't believe that..

"T-Tell me the t-truth! What d-did you do to her?" You rose your voice a little, trying to sound confident.

"...I wish I wasn't telling the truth, child. Beyond this place lies the rest of the Underground...It is not safe for anyone, nevermind a young child. But alas...I-I could not protect them from the horrors...I didn't have it in me to take the life of a child so similar to..." Her voice trailed off, becoming an inaudible whisper. "...Just go, child, down the stairs into the basement. You will find a door at the end. Go through that door. Find your sister..Make sure she is safe. But be aware, the rest of the Underground will not be so forgiving."

You blinked. What did she mean by that...? Was it only going to get worse? You shook your head, no, she was probably just telling you that to scare you..Yeah, that was it. It couldn't possibly get any worse than this.

Right..?

You pushed these thoughts aside, walking forward cautiously, then bolting down the staircase as fast as your legs could carry you, and just ran, only ever slowing down to turn around the corner, and make your way towards a massive door..

 


End file.
